1. Field of the Invention
The present invention relates to a method for aligning a cylindrical laser optical resonator and more particularly to a method for aligning a high extraction decentered annular ring resonator (HEXDARR).
2. Description of the Prior Art
Various types of lasers are known in the art. For example, chemical lasers are known. Examples of such chemical lasers are disclosed in U.S. Pat. Nos. 3,575,669; 3,992,685; 4,237,429; 4,514,698; 5,099,492; and 5,624,564, hereby incorporated by reference. In order to provide relatively high power lasers in a relatively compact configuration, lasers utilizing a cylindrical gain generator and an annular ring resonator have been developed. In such lasers, the cylindrical gain generator is disposed within an annular ring resonator. In such a configuration, the gain medium flows radially outwardly from the cylindrical gain generator into an annular gain volume of the cylindrical resonator. In order to extract the maximum amount of power from the annular gain volume, high extraction annular ring resonators have been developed, for example, as disclosed in U.S. Pat. Nos. 4,598,408 and 4,744,090, assigned to the same assignee as the present invention hereby incorporated by reference. Examples of other annular ring resonators are also disclosed in U.S. Pat. Nos. 4,606,036 and 4,516,214. The annular ring resonators, for example, as disclosed in the '408 patent, include a conical rear reflector, a waxicon, a reflaxicon, a scraper mirror with a decentered aperture and a plurality of flat beam steering mirrors forming a compact leg of the resonator. The decentered aperture in the scraper mirror allows a circular beam of light to be transmitted therethrough and reflected in the compact leg of the waxicon. The waxicon expands the circular beam into an annular light beam which makes a first pass through the annular gain volume. The annular beam is reflected by the conical rear reflector and thus makes a second pass through the annular gain volume. The annular beam reflected from the rear reflector is reflected to the reflaxicon, where the beam is compacted and a portion thereof reflected through the decentered aperture of the scraper mirror as feedback with the balance of the beam outcoupled as an output beam.
While such annular ring resonators provide relatively high gain, such resonators are not without disadvantages. For example, the alignment of the various optical surfaces within the resonators have heretofore been relatively difficult and require much more precision than standard spherical optical surfaces. Unfortunately, relatively small amounts of misalignment of the optical surfaces causes significant degradation of the optical quality of the coupled laser beam.